Construction of the ether-linked methyl 5aЈ-carba-β-lactoside (3) and N-acetyl-5aЈ-carba-β-lactosaminide (4) were carried out starting from the coupling products 15 and 16, readily obtained by coupling between 1,2-anhydro-4,6-Obenzylidene-5a-carba-D-mannopyranose ( 7) and the oxide anions generated from methyl 2,3,6-tri-O-benzyl-β-D-glucopyranoside (8) and methyl 2-acetamido-3,6-di-O-benzyl-2deoxy-β-D-glucopyranoside (10), respectively. Their 5acarba-α-D-mannopyranose moieties were transformed into those of 5a-carba-β-D-galactopyranose by a sequence of reaction: Oxidation of the 2Ј-OH group, epimerization of the C-1Ј with DBU, selective reduction of the carbonyl group, and epimerization of the C-4Ј via oxidation and then reduc-In a family of pseudo-disaccharides, carbadisaccharides [2] bonded by an imino linkage have been shown to possess interesting biological activities: e.g. inhibitory potency against glycosidases as seen in α-glucosidase inhibitor α-methyl acarviosin, [3] trehalase inhibitor validoxylamine A, [4] 5a,5aЈ-dicarba-α,α-trehalose, [5] and so on. Whereas, ether-linked carbaoligosaccharides [6] [7] [8] [9] have been shown to act rather as substrate analogs for some glycosyltransferases involved in oligosaccharide-chain biosynthesis.
Synthesis [10] of biologically interesting ether-linked 5aЈcarbadisaccharide analogs 3 of methyl β-lactoside 1, together with the ether-and imino-linked analogs 4 and 5 of methyl N-acetyl-β-lactosaminide 2, was reported herewith. These compounds have initially been designed and synthesized, being expected to act as disaccharide mimics useful as potential enzyme-inhibitors against β-galactosidases and/or galactosyl transferases involved in the biosynthesis of complex oligosaccharide-chains of glycolipids.
Construction of ether-linked carbadisaccharides 3 and 4 was carried out starting from the coupling products of carba-sugar donor 1,2-anhydro-4,6-O-benzylidene-5acarba-β--mannopyranose [8] (7) and the respective O-benzylated sugar derivatives 8 and 10, followed by consecutive epimerizations [9] at C-1 and 2 (α-manno Ǟ β-gluco configuration), and at C-4 (β-gluco Ǟ β-galacto configuration). On [᭛] Part 38: Ref. [1] .